SurfaceListBox isSelected - System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor

Question

I have a surfacelistbox with the following style:

<s:SurfaceListBox.ItemContainerStyle>
    <Style TargetType="s:SurfaceListBoxItem">
        <Setter Property="HorizontalContentAlignment" Value="Center" />
        <Setter Property="HorizontalAlignment" Value="Center" />
        <Setter Property="FontSize" Value="13" />
        <Setter Property="Foreground" Value="Black" />
        <Setter Property="FontWeight" Value="Normal" />
        <Setter Property="RenderTransformOrigin" Value="0.5,0.5" />
        <Setter Property="MinHeight" Value="30" />
        <Setter Property="Template">
            <Setter.Value>
                <ControlTemplate TargetType="{x:Type s:SurfaceListBoxItem}">
                    <ContentPresenter />
                </ControlTemplate>
            </Setter.Value>
        </Setter>
        <Style.Triggers>
            <Trigger Property="IsSelected" Value="True">
                <Setter Property="HorizontalContentAlignment" Value="Center" />
                <Setter Property="HorizontalAlignment" Value="Center" />
                <Setter Property="FontWeight" Value="Bold"/>
                <Setter Property="Foreground" Value="#FF7E0123" />
                <Setter Property="RenderTransform">
                    <Setter.Value>
                        <ScaleTransform ScaleX="1.25" ScaleY="1.25"/>
                    </Setter.Value>
                </Setter>
            </Trigger>
        </Style.Triggers>
    </Style>
</s:SurfaceListBox.ItemContainerStyle>

I am populating this surfacelistbox through code and then adding a "Show All" item:

private void AddShowAllCategories(int totalItems)
{
    SurfaceListBoxItem CategoriesListBoxItem = new SurfaceListBoxItem();
    CategoriesListBox.Items.Insert(0, CategoriesListBoxItem);
    CategoriesListBoxItem.Content = "Show All " + "(" + totalItems + ")";
    CategoriesListBoxItem.Margin = new Thickness(0,30,0,0);
    CategoriesListBoxItem.IsSelected = true;  //This is what is causing the issue
}

Everything works fine and I get no errors until I set the IsSelected to true through code. I then get this error:

System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor, AncestorType='System.Windows.Controls.ItemsControl', AncestorLevel='1''. BindingExpression:Path=HorizontalContentAlignment; DataItem=null; target element is 'SurfaceListBoxItem' (Name=''); target property is 'HorizontalContentAlignment' (type 'HorizontalAlignment')

If I dont set IsSelected to true through code and instead click on an item, everything is fine. Any ideas?

Eran Sakal Eran Sakal · Accepted Answer · 2012-08-21T05:19:23

Since you didn't provide the code behind that select an item using code, I cannot know if you are using MVVM, working with code behind or whether you already tried the below methods.

I followed your scenario and managed to select an item from code using 'ItemContainerGenerator':

        // Selecting an item given the actual item
        object requestedItem = null; // TODO - You should set here the actual item
        SurfaceListBoxItem itemContainer = itemsList.ItemContainerGenerator.ContainerFromItem(requestedItem) as SurfaceListBoxItem;
        itemContainer.IsSelected = true;

        // Selecting an item given his index in the item source
        SurfaceListBoxItem itemContainer2 = itemsList.ItemContainerGenerator.ContainerFromIndex(2) as SurfaceListBoxItem;
        itemContainer2.IsSelected = true;

Use the first method if you have a reference to the item you want to select and the second if you only know the index in the provided list.

Let me know if it worked for you.

Eran.

SurfaceListBox isSelected - System.Windows.Data Error: 4 : Cannot find source for binding with reference 'RelativeSource FindAncestor

1 Answers